A Rotten Swahili is when you go down on a nersy chick and based on the smell an/or foreign pubic hair in her vaginal region you can extrapolate that she is in fact a mudshark.
You totally deserve the rotten swahili that my momgave you the other night bro.
swah-hee-lee-an bak-slap When receiving oral while standing, right before ejaculating, the person receiving oral defecates on their hand, and proceeds to slap it on the back of the person who is giving the oral.
Lilly: "So like omg, i was giving head to Billy and right before he came he took a shit in his hand and slapped it on my back!"
Leah: "LMAO he so gave you a swahilian backslap!"